Background/Context: The type of professional development provided for teachers has been undergoing change from a one-time workshop approach to a more embedded, long-term, reflective, and collaborative structure. Although findings on the impact of new forms of professional development (PD) are beginning to emerge in the literature, there is little research on the professional development of those who design and support these PD efforts. Purpose/Objective/Research Question/Focus of Study: To better understand how to support secondary teachers' engagement in collaborative inquiry, a group of 12 professional development providers deliberately set out to use the same processes and structures in their development and implementation of a PD model. This research examines what this group learned about fostering and sustaining a culture of collaborative inquiry and considers how this can inform PD providers' support of teachers' engagement in a collaborative inquiry cycle. Research Design: A narrative case study design was used to examine the evolution of the professional development group from its inception in March 2004 through December 2005, halfway through the project's duration. The particular timeframe was targeted to explore the developmental phase of the group and critical decisions that shaped the group structure and direction. Data Collection and Analysis: Traditional qualitative data sources were collected and analyzed in the construction of the narrative, including interviews with the professional developers, archived documents, and video and audio recordings of meetings. Conclusions/Recommendations: The PD group's focus on how to foster and sustain a culture of collaborative inquiry provides insights into the structures and processes that support this kind of collaborative endeavor. Assuming an inquiry stance toward the work was challenged by the ongoing business of implementing a large-scale project and the demands of people's other work in school districts and universities. Difficulties related to communication between and during meetings also occurred. An explicit reliance on collaborative norms and explicitly using processes such as dialogue structured by protocols, distributing leadership responsibilities, and co-constructing an inquiry focus based on data analysis helped the group develop and maintain an inquiry stance. These findings inform the support of teachers undertaking collaborative inquiry for professional growth